An EUV lithography method using extreme ultraviolet (EUV) to perform the transfer of microscopic patterns is proposed.
In the manufacturing of a reflective mask used for the EUV lithography method, a reflection layer, a capping layer (also called a stopper layer etc.), and an absorption layer are sequentially formed on the major surface of a substrate, and the absorption layer is processed by dry etching; thereby, a pattern region including a desired pattern is formed. Then, the absorption layer, the capping layer, and the reflection layer are processed by dry etching to form a light blocking region (also called a light blocking frame etc.) surrounding the pattern region.
Here, in the manufacturing of the reflective mask, the resist mask used in the dry etching processing of the absorption layer is removed by dry ashing processing using oxygen plasma or we ashing processing using sulfuric acid (e.g. see Patent Documents 1 and 2).
However, if such ashing processing is performed in the case where the capping layer is formed of ruthenium (Ru), there is a problem that the optical characteristics of the capping layer may be changed.